
The virtual element functions in the local space \(V_{h}^{\operatorname{node}}(K)\)  for all \(K\in \Omega _{h}\)  are uniquely determined by the set of their vertex values over \(\partial K\) ;
see, e.g., [1]} for a proof of their unisolvence.
We introduce the global nodal space
\( V_{h}^{\operatorname{node}}:=\lbrace  v_{h}\in \mathcal {C}^0(\overline{\Omega })\mid v_{h}{}_{|K} \in V_{h}^{\operatorname{node}}(K) \; \forall K\in \Omega _{h}\rbrace ,\) 
